Aerofoil construction



Aug. 11, 1931.

L. G. YOUNG AEROFOIL CONSTRUCTION Filed June 21, 1929 3 Sheets-Sheet l 06m 00 H1111. m: 6. 151mg, 55

I M 6111 41121 1 1 ywi Aug. 11, 1931. L. G. YOUNG AEROFOIL CONSTRUCTIONFiled June 21, 1929 3 Sheets-Sheet 2 M O fa wfluw umnu (Miami 1 M 0 Aug11, 1931.

L. c. YOUNG 1,818,519

AEROFOLL CONSTRUCTION Filed June 21. 1929 a Sheets-Sheet 3 Awe/Mm:

b a. 161: M (51 [WW/um Patented Aug. 11, 1931 PATENT OFF CE LEWIS G.'YOUN G, OF BRONXVI LLE, NEW YORK 1 ennororn cons'rnuorron n' pn'c'atidnfiled June '21,

. This -inventionrelates to the construct-ion of aerofoils or'aeroplane- Wings, and -is*'particularlyjconcerned With the proyisi'orrof a spar forinternallybracing a wing Which is I curved along its-"span;

Itha's beenfound that af laterally curved wing'tvhich has its 'niai-nlifting surface relativ'e'l y near the fuselageof the aeroplane, and"Which has a" stabilizing surface merging 10 with the lifting.surface-and extending laterally-therebeyond, is very difiiculttoconstruct,- especially" when a dihedral angle exists-between saidsurfaces. In fact it has 1 hitherto been thought impossibleto brace 15adequatelysu'c'h a-wi'ngmer'ely by the use of internal bracing. Thepresent invention resides, therefore, in the proyi'si'on"of spars forWings Whose surfaces are curved later- 1 any, which s 'aar is li ght inWeight and easy 20 to manufacture, which" has a high factor of safety;which is Wholly internal of the wing, and WlllCh takes such" form thatthe wing surfacesi conform to the upper' and loWeredges thereof, wherebythe wing may assume the best outward contour ram lift as Wellas"stability.- I

Specifically, the main feature of the inventiefi consistsfin a spar forinternally bracing a WingyVhOSe mainlifting surface 80 makes "a dihedralaegis with the stabilizing surface"; whereby the controlof the planebecomes-practicallyautomatic, Without at the-sa ine timeanysacrifice-{or speed, lift, or safety, and" avoiding external orinsufficient bran" Other"objects and advantages will be ap-Piiiefitfffihith following detailed descrip tion or awareness-embodimentof my inven tion 1connection with the accompanying nmvungs wnsrein: iFig-urel 'isfa pla'n View of a Wing constrnetd according to the presentinvention. Figure 2 isa front elevation of the Wing. Figure" 3 isaffrontview" 'of the forward sparsho' 'in Figiirel. 1 Figure's'wr to' 1Oinclusive, are cross secti onsof the wing-taken on the lines 4'4;'to IOQIO inclusive, in Figure '1, and looking inthe direction of the arrows;

66 4 Figure 11 isa front'view of a single Wing 1929; Serial No. 372,650.

spar'extending on both sides ofthe' fuselage.

Figure 12 is a cross section of'th'e Wing taken on the line 4-4 ofFigure 1, and showingaunodified form of construction.

It Will be understood that throughoutthe description the termlongitudinal refers toa dimension fore and aft of theaeropl'ane', Whilelateral means Widthivis'e or along the Wingspan thereof.

In a" general sense each Wing. has a sup; porting surface adjacent tothe body and to the front edge of the Wing, With'a longitudinallystabilizing surface to the rear of the supporting surface and alaterally stabilizing surface at the side or toward the tip of the Wingremote from the fuselage. The supportingsurfaces are so 'curyed' thatthe pressure resultants of the two surfaces, Whether the flying machinebe inclined' in onedirect'ion or the other,'meet at a point in aline-above th'ecenter of gravity offthemachine and although the distanceof thecehter ofpressure of one'wing from thelon'gi tud-inal axis of themachine Varies inversely as the distance of the center pressure of theother Wing in a bank, the resultant of the upward pressure against thelowermost Wing is in'creased'while that against the uppermost wing isdecreased, and the machine is therefore returned to a position ofequilibrium. Moreoverit has been found, in the present instance, that itis desirable to pre servein the'structure of themachine ad'efiniterelationship; thus, if the main partof each wing, as Will beexplained hereinafter, has a ratio of length (in a lateral directionfromthefuselage') to chord (in a longitudinal direction) of'two toone,then thedi's tanc'e's of the'center ofpressure of the laterallystabiliiing surface and of the center of 0 upwardpressure' on theunderside of'the Wing from the longitudinal axis should also beintlieratio of two to one, and the'-dis tan'ces of the center of pressureof"the longitudi nally stabilizing surface and of thecenr ter" of upwardpressure on the supporting surface from the lateral axis should alsobeinthe ratio of two to one.

' In accordance With the invention each- Wing or'aerofoilhas adjacent tothe fuselage or longitudinally of the machine and its own forward edge asupporting surface, concave below, curved both in a longitudinaldirection and in a lateral direction, with a reversely curvedlongitudinally extending stabilizing surface to the rear and a reverselycurved laterally stabilizing surface at the side remote fromthe body,the centers of pressure of these surfaces having, as already indicated,substantially the same ratio 'of distances from the longitudinal axisand from the lateral axis as that which the length of the wing portionhas, in a general sense, to its width.

It will be understood that the two wings are symmetrical with respect tothe longitudinal axis of the machine and a description of one willsufiice for the other.

There is shown at w a wing constructed in accordance with the presentinvention. This wing consists, generally, of a lifting portion, beingthe part between the lines 44 and 88 of Figure 1, and a stabilizingportion being the part shown between 88 and the wing tip. This wing isconnected tothe fuselage of the plane at 44, and is provided withsupporting spars a and a and with ribs 6. The leading edge of the wingis at 0 and the trailing edge at 0?, the usual supporting members 0 andcl being provided adjacent the leading and trailing edges. The wing isshown as tapering,,generally, to a point e at the wing tip. In. thecross sectional views in Figures 4 to 10 inclusive, there is shown awing tapering in thickness and having a particular surface as will bedescribed in detail below.

As the particular curvature of the wing along its span is of the utmostimportance, the exact positions of the wing with reference to a givenplane determined by the lines 5-8, in Figure 3 and ss in Figures 4 to 10is shown in great detail. It will be seen that the wing makes betweenits ends what may be termed a dihedral angle. That is, looking atthefront elevation of the wing, there is at first an upward curve. Thewing then curves downwardly to form a depressed portion between itsendsand then curves up slightly, preferably not reaching, however, aheight as great as the first raised portion assumes. This is shown bestin Figures 4 to 10, wherein the reference lines ss are horizontal and ina plane passing through the lower front corner of the spar a;

Since it is the particular construction of the spar which constitutesthe main feature of the pr'esent'invention, the spar a is shown indetail in Figure? The spar a is similar in construction to the spar aand takes positions relative to the latter as shown in Figures4 tolO.

The upper and'lower wing surfaces are of course, designed with generallystream line form, but the lower surfaces have more particularly aconcave portion m and a con vex portion a, the former being forward ofthe point kat which the curve reverses and the latter being to the rearof said point. It will be noted that the curve m is approximately twicethe length of the curve a, though this proportion is not absolutelyessential. However, when these curves are in a given ratio at one wingsection, the ratio should be preserved at the other wing sections. F or.convenience in description of the definite relationship between thelifting portion of the wing and the stabilizing portion, it may be notedthat the liftin portion between lines 4-4 and 88 is of trapezoidal shapewith long sides of approximately twice the length of its short sides.This approximate ratio of two to one between the lengthand the width ofthe lifting section is the ratio which determines the locations of thecenters of pressure, whereby the plane is properly balanced. It will beunderstood, of course, that this definite relationship is approximateonly and is not absolute. The other portion of the wing, from the line88 to the wing tip comprises the stabilizing portion of the wing and hasa leading edge which sweeps back to the wing tip which is approximatelyin line laterally with the trailing edge ,of the wing at the fuselage. I

Although the wing is shown as tapering in thickness from the fuselage tothe wing tip, a wing of constant thickness is also within the scope ofthis invention. It will also be apparent that the .wingsma-y form adihedral angle between them or lie in generally the same plane, and mayhave sweep back or make any desired angle with the line of flight. Thewing spars, of course, need not be located exactly in the position shownnor have the same relative lateral dimensions but may bevaried providingthe wing curves shown are generally maintained. Although wooden sparsare shown in Figures 4 to 10. inclusive, metal spars as shown in Figure12 could be used instead. The particular type of rib used forms no partof the present invention.

In Figure 11 there is shown a singlespar extending on both sidesof thefuselage f and having a section a connecting'thetwo sections a, each ofwhich latter is constructed according to thefpresent invention; Thetendency of forces applied to the wings of the usual straight wingedmachine, when equilibrium is disturbed, is to tip the machine farther inthe same direction. In the present machine, however, by reason of thecurvature of the wing not only do the centers of sustainingpressureof'the two wingsthat is, the points at which the sustainingpressures act, shift with varying positions of the machine but theresultants sures themselves exerted against the under? sides of the twowings are also varied although the resultants still meet in a line drawnvertically through the center of gravity of the machine and above thecenter of gravity, so that the machine continues in a condition ofindifferent stability but with an increased pressure resultant againstthe lower wing which tends to restore the machine to a position ofequilib rium. Of course, as the machine tilts upward on one side thecenter of sustaining pressure on that side moves farther from thelongitudinal axis of the machine and its leverage increases, althoughthe resultant of the sustaining pressure on that wing still meets theresultant of the sustaining pressure on the other wing in the verticalline drawn through the center of gravity of the machine, and suchresultant is relatively reduced.

Although the machine still remains in indifferent stability after itsequilibrium has been disturbed, with a tendency to return to a positionof equilibrium, as already explained, it is desirable to provide othermeans to restore the equilibrium. This is accomplished automatically bythe stabilizing surfaces. ward or downward, on the stabilizing surfaces,or rather the preponderance of pressure upward or downward, depends uponthe inclination of the machine. If the machine dips downward from thepredetermined angle of normal flight, so that the preponderance ofressure is exerted upon the upper side of t e longitudinally stabilizingsurface, then the center of pressure downward will be located in rear ofthe center of sustaining pressure and at a distance in rear of thelateral axis, as compared with the distance of the center of sustainingpressure, in the predetermined relationship, that is, in the wing shown,in approximately the ratio of two to one. With its greater leverage oftwo to one the stabilizing pressure will quickly correct the disturbingfactor of pressure and restore the machine to its position ofequilibrium. In like manner, if the machine tilts upward too much, thepreponderance of pressure on the stabilizing surface will be exertedagainst the underside of the wing and in the same relationship so thatthe machine will be returned to its position of equilibrium. It will beunderstood that by reason of the curvature of the sustaining surface ofthe wings in a longitudinal direction, the resultants of the sustainingpressures exerted against the two wings continue to meet in a verticalline drawn through the center of gravity of the machine, for allordinary disturbances of position, whether the machine dips downward orupward in a longitudinal direction.

In like manner when the machine is tilted The direction of pressure, up-

laterally to one side a pressure is exerted against the upper laterallystabilizing surface of the wing on the upper side and as the center ofsuch surface has a definite relation through the supporting andstabilizing surfaces on the other side of the plane, the leveragethrough which the laterally stabilizing pressure acts is greater thanthat of the sustaining pressure on the same side and the machine will bethereby restored to its position of equilibrium. The action of thelaterally stabilizing pressure against the higher wing, when the machineis tipped laterally, is supplemented by an increase of sustainingpressure on the lower side through the direction of the flow of air, inthe manner hereinbefore explained, under the lower wing into the regionof the sus-' taining surface adjacent to the body of the machine.

The plane may be positively controlled by ailerons, rudder andelevators, not shown. Other details of the construction of the plane arenot shown as they do not form any part of the present invention.

Further, applicant does not wish to be limited to the specificembodiment shown, save as defined in the appended claim.

I claim as my invention:

In an aeroplane, a unitary spar internally disposed in the wing, saidspar being laterally straight and being alternately raised above anddepressed below a given horizon; tal plane, the portion adjacent thefuselage being raised with respect to the fuselage.

This specification signed this 5th day of June, A. D. 1929.

LEWIS G. YOUNG.

